Most of the bar code readers currently in widespread commercial use are designed to emit a beam of laser light which is swept across a target in a single or multiple scan. A detector, which is tuned to the same frequency as the emitter, is focused on the region being scanned or swept by the emitting beam of laser light. As the beam moves over a dark bar, the intensity of the signal received by the detector drops. As the beam moves over a bar which is lighter (preferably, white) the intensity of the received signal increases. This digital bright-dim or on-off sequence carries the recorded information, usually translated into a string of numbers. Black and white bars tend to generate the best differentiation in intensity, however, any high reflective color paired with a much lower reflective color will generally suffice.
Portable electronic devices, such as wireless cell phones, PDA devices, pagers, or combinations of these and other devices, are in widespread use. Most such portable electronic devices include a display screen for displaying information and pictures on them. Most electronic devices, and in particular cellular phones produced in volume for general use, employ screens designed primarily for viewing based on the light actively emitted by the screen, and not on reflected light.
In addition, the predominant technology employed in the manufacture of such screens is a back-lit LCD screen. A back-lit LCD screen employs multiple layers of polarizing material and liquid crystal filters to control the amount of light transmitted from an underlying light source as the light passes outwardly through a multitude of filtering layers. Because the emission of a bright line on part of this display does not necessarily correlate to an increase in surface reflectivity, and vice-versa, bands of light and dark are not consistently or accurately read by laser-based reflection sensing scanners. The multiple layers of materials used in back-lit LCD screens also produce strong reflections which are not effectively modified by changes in the underlying layers which produce the changes in the outwardly transmitted light. As a consequence, many bar code readers presently in commercial use at retail and point-of-sale operations are not able to accurately read visual images including a bar code pattern of bars or squares when such bar codes are displayed on the screen of a portable electronic device, such as a cell phone.
The ability of existing scanner systems to receive bar code information displayed on a cell phone screen, without alteration of the point of sale (POS) scanner systems themselves, is a commercially desirable goal.